Temperature Stabilized Heating System For Spa

ABSTRACT

A spa tub includes a control system that operates with a water temperature modification system to stabilize the spa water at a set temperature. In a preferred embodiment, the water temperature modification system is a heat pump. The stabilized temperature provides safety to users of the spa.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Ser. No. 11/379,859,filed Apr. 24, 2006, which claims the benefit of U.S. Provisional App.No. 60/596,648, filed Oct. 10, 2005, both of which are herebyincorporated by reference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates broadly to spa and systems for temperaturecontrol thereof. More particularly, this invention relates to a spaincorporating a heat pump system to both heat and cool the spa water.

2. State of the Art

Spas, in the form of a hot tub or larger swim spas, are generally heatedby electric heaters. An electric heater is employed to heat the watertemperature to a temperature as set by a user through a user interface.The interface triggers a controller to operate the heater. After thewater temperature reaches the set temperature, the controller stops theelectricity supply to the heater. Over time, the water temperaturedecreases due to heat loss to the ambient through the spa tub insulationmaterial and by direct heat loss at the water surface. When the watertemperature reaches a certain temperature below the set temperature, theelectric heater again heats the water. Heating via electricity can bevery inefficient. For example, the typical electric spa heater requires5.5 kW, powered at 23 amps which, with the high cost of electricalenergy, can be very expensive to run.

In a hot geographical region, it may be beneficial for a spa tub to havecooling capability to cool the water to a set temperature below ambienttemperature. One spa that provides such functionality is the AteraAnytemp Spas™ from Four Seasons Home Products, Inc. of Phoenix, Ariz.This spa includes a 4.3 kW electric heater to heat the water and aseparate 6000 BTU water chiller to cool the water. Both the electricheater and water chiller are energy inefficient. In addition, thissystem heats the spa water no faster than a conventional spa heater.

Heat pump systems have been used to heat the water in pools moreefficiently than electric heaters. In addition, U.S. Pat. No. 5,509,274to Lackstrom describes using a heat pump to both heat and cool ambientair in an environment associated with a pool or hot tub heated by theheat pump. However, a heat pump has not been effectively used to bothheat and cool the water in a spa tub.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a spa with aheating and cooling system which is energy efficient in a standard modeof operation.

It is another object of the invention to provide a spa with a heatingand cooling system which has a rapid heating mode of operation that issignificantly faster than a conventional electric heater.

It is also an object of the invention to provide a spa with a heatingand cooling system to provide temperature stabilization capacity.

It is still another object of the invention to provide a spa that has aprogrammable timer to allow fixing the spa water temperature at adesired time.

In accord with these objects, which will be discussed in detail below, aspa is provided with a heat pump system for both heating and cooling thewater contained in the spa tub. The spa includes a tub, a plurality ofjets within the tub wall, a suction fitting, associated plumbing, and awater pump to circulate out of the tub through the suction fitting,through the plumbing and back through the jets under pressure back intothe tub. As the water is sent to the jets it is moved through a venturiwhere air from a supply is entrained within the water. A cabinetsupports the tub and encloses the workings of the spa.

The heat pump includes a compressor, a water heat exchanger, anexpansion device, an ambient heat exchanger, connective plumbing, afour-way valve enabling a preferred reversible operation, and a workingfluid (refrigerant) therein. In accord with a preferred aspect of theinvention, the heat pump uses the existing water pump of the spa tocirculate the water through the water heat exchanger of the heat pump.The heat pump can be operated to raise or decrease the water temperatureor maintain water temperature.

It is recognized that the ambient heat exchanger of the heat pump willproduce condensate. In distinction from systems that are solely intendedto be used outdoors, the removal of condensate from the heat pump is anissue when the spa system of the invention is adapted for indoor use.Without proper removal, such condensate may cause water to runoff intoan indoor home space and cause associated wet spots, water damage and/ormold and mildew. In accord with one preferred aspect of the invention,plumbing is provided to couple condensate collection to the venturi atthe water jets. Thus, negative pressure created at the venturi duringwater jet operation causes automatic removal of condensate from the heatpump and provides it into the spa tub.

In accord with another preferred aspect of the invention, the ambientheat exchanger during operation automatically periodically cycles offand on to prevent and/or remove frost build-up on the heat exchangecoils thereof.

In accord with a yet another preferred aspect of the invention,components of the heat pump are subject to noise reduction. Such noisereduction may include physical masking by acoustic isolation and/orinsulation. Alternatively, the noise reduction may be implementedelectronically.

The spa and cabinet together define a space therebetween. In accord witha further preferred aspect of the invention, a diverter is providedwhich directs air which is most efficient for use to the ambient heatexchanger. For example, air from the space may be pulled when it iswarmer than ambient air, and ambient air may be pulled when warmer thanair in the space or when pulling air from the space would result inother thermal inefficiencies (e.g., excessive cooling of the spa tubwater).

The spa preferably includes an ozonator, which is known in the art tocontrol bacteria and otherwise filter the water. The ozonator requiresan infusion of dry air for optimal operation, as dry air accepts moreozone for delivery to the water. In accord with another aspect of theinvention, drier air from the cool side of the ambient heat exchanger ofthe heat pump is drawn off and sent to the ozonator to optimizeoperation of the ozonator.

In accord with an additional preferred aspect of the invention, the spaalso includes a conventional electric heater that can be activated inconjunction with the heat pump to provide a rapid heating mode. Becausethe water is brought up to the desired temperature more rapidly and thenmaintained at the desired temperature with the higher efficiency heatpump, overall energy efficiency is increased. In a preferred embodiment,the heater coil of the electrical heater is integrated with the heatpump.

In accord with yet another aspect of the invention, a heat pump andtemperature control system can be retrofit to an existing spa such thatthe heat pump is located outside the cabinet of the spa and plumbing isused to circulate water to the heat pump or refrigerant into the cabinetof the spa.

In accord with still another aspect of the invention, a control systemis provided for a spa system such that the user of the spa can program aset time into the control system such that the water in the spa reachesa user specified temperature at the set time.

Additional objects and advantages of the invention will become apparentto those skilled in the art upon reference to the detailed descriptiontaken in conjunction with the provided figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective of a spa tub system according to the invention,with a portion of the cabinet shown in partial section to revealcomponents of the water circulation system and water temperature controlsystems;

FIG. 2 is a schematic of the spa tub, hydrotherapy jet circulationsystem and water temperature control systems;

FIG. 3 is a schematic of one embodiment of a water temperature controlsystem according to the invention;

FIG. 4 is a schematic of another embodiment of a water temperaturecontrol system according to the invention;

FIG. 5 is a schematic of circuit for control of a water temperaturecontrol system according to the invention;

FIG. 6 is a schematic of a retrofittable heat pump system according tothe invention; and

FIG. 7 is a flowchart of an algorithm for controlling water temperaturewithin a spa tub.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to FIGS. 1 and 2, a hot tub spa system 10 is shown. Thesystem 10 includes a hot tub 12 formed as a molded shell defining steps14 into the tub, a floor 16, seating areas 18, 20, 22, 24, 26, and anupper rim 28 among other features. The spa includes a hydrotherapysystem 30 comprising a plurality of jet assemblies 32 situated withinthe shell of the tub 12 at the seating areas 18, 20, 22, 24, 26, asuction fitting 34, associated plumbing 36, and a water pump 38 tocirculate water out of the tub through the suction fitting, theplumbing, and back through the jet assemblies 32 under pressure into thetub 12. As the water is sent to the jets 32, it is forced throughventuri where air from an air source 39 is entrained within the watersuch that when the water is ejected by the jet, it is aerated. A cabinet40 surrounds the tub 12 and encloses the hydrotherapy workings of thespa. The spa may also be associated with stairs 42 leading into the spafrom an interior floor or exterior ground surface and one or moresitting benches 44, planters, etc.

Referring to FIGS. 2 and 3, the spa is provided with a heat pump 50 forheating and cooling the water contained in the spa tub 12. The heat pump50 includes a compressor 52, a water heat exchanger 54, an expansiondevice 56, an ambient heat exchanger 58, connective plumbing 60, afour-way valve 62 enabling a preferred reversible operation, and aworking fluid (refrigerant) therein. As discussed further below, thewater pump 38 for the hydrotherapy system 30 routes tub water throughthe water side heat exchanger 54 to effect heating or cooling of the spatub water. Thus, no separate water pump is required to circulate thewater through the heat pump 50. The heat pump 50 can be operated toraise or decrease the water temperature or maintain the watertemperature at a set temperature.

In a water heating mode, the compressor 52 compresses a working fluid(refrigerant) and discharges the fluid through the four-way valve 62.The working fluid then enters the water heat exchanger 54 and heats thewater. Inside the water heat exchanger 54, the working fluid is cooledand condensed. The condensed working fluid expands in the expansiondevice 56 becoming low temperature and low pressure. The low temperatureworking fluid enters the ambient heat exchanger 58 absorbing heat fromthe environment. Inside the ambient heat exchanger 58 the working fluidevaporates using the heat from the environment. The working fluid vaporflow through the four-way valve 62 then enters the compressor 52. In acooling mode, the working fluid flow direction is reversed by thefour-way valve 62 such that heat is absorbed at the water heat exchanger54 and removed at the ambient heat exchanger 58. The four-way valve 62is operated by a solenoid, and the flow direction inside the four-wayvalve 62 is determined by whether or not the solenoid is in an energizedstate, as set by a controller 102, discussed below with respect to FIG.5. This four-way valve mechanism allows for easy reversal of the workingfluid flow direction when the controller is triggered for switching themodes, as discussed below.

The heat pump 50 is energy efficient relative to a standard electricresistance heater. As a result of the low working fluid temperature atthe ambient heat exchanger 58, heat is absorbed from the ambient. Thisheat is used to evaporate the working fluid. During the evaporation, theenergy of the working fluid is increased. The evaporated working fluidis compressed at the compressor 52. During the compression process, thecompressor 52 requires external energy (electricity), and this energy isadded to the working fluid. The absorbed energy from the ambient and theadded energy at the compressor is transferred to the water at the waterheat exchanger 54. Typically, the absorbed energy at the ambient heatexchanger 58 is larger than three or four times the required energy forthe compressor 52, and this results in a heating system three to fourtimes more efficient than a standard or conventional electric resistanceheater for a spa tub. The heat pump is inherently more efficient than aconventional resistance heater because it uses energy only to remove andtransport heat from the ambient to the spa water, not create the heatusing resistance heating. Since the heat pump removes heat from theambient for heating, its efficiency depends on the temperature of thesurrounding ambient. In hot climates, such as the southern UnitedStates, the heat pump can be up to five times more efficient than aresistance heater. In cooler climates, such as the northern UnitedStates, the heating efficiency of the heat pump relative to theresistance heater falls to three times more efficient or less. If theheat pump is a ground source version, since the ground temperature staysrelatively constant, the efficiencies of the heat pump stay about thesame in all parts of the country at about five times more efficient thanthe resistance heater. By way of example, the heat pump uses 1 kW (110Vat 10 amps), whereas the resistance heater uses 5.5 kW (220V at 23amps).

As an example of external maintenance of heating sources, the heat pump50 is preferably electrically powered and in a preferred embodiment theambient heat exchanger 58 is an air heat exchanger. Such air heatexchangers can be mounted internally; i.e.; within the spa tub cabinet40, or can be mounted externally of the spa tub 12 within a separatehousing but coupled to the water heat exchanger 54 within the cabinet 40and/or other plumbing within the cabinet through appropriateconnections. Air heat exchangers are efficient in relatively warmerclimates. Alternatively, the ambient heat exchanger can be a groundsource heat exchanger which has the advantage of pulling heat from theground rather than the air and is generally more efficient in allclimates, but requires a more extensive installation. The ground sourceheat exchanger can be mounted directly beneath or adjacent the cabinetor spaced apart therefrom, e.g., in a separate housing. The separatehousing for any of the described ambient heat exchangers may be thestairs 42, the benches 44, planters associated with the spa, or otherstructures.

In addition, cool air from the cold side of the ambient heat exchanger58 can be piped through an insulated container 66 mounted within oradjacent to the spa tub cabinet which is used as a refrigerator for foodor beverage, or can be routed for use as a bottle chiller 62 integratedinto the spa tub shell. Warm air from the warm side of the ambient heatexchanger 58 can be piped to a towel warmer 68; i.e. an at leastpartially enclosed housing including towel hooks or bars, which isintegrated into the spa cabinet.

It is recognized that the ambient heat exchanger 58 of the heat pumpwill produce condensate. In distinction from prior art gas and electricfired heat pump systems that are specifically designed to heat largeswimming pools and are solely intended to be used outdoors, the removalof condensate from a heat pump is an issue when the spa system of theinvention is adapted for indoor use. Such condensate may cause water torunoff into an indoor home space and cause associated wet spots, waterdamage and/or mold and mildew, unless properly removed. In accord withone preferred aspect of the invention, the heat pump 50 (or at leastambient heat exchanger 58) is mounted at an angle (e.g., from the spashell or to a wall of the cabinet) to cause gravity feed drainage ofcondensate from the unit. The condensate is collected in a reservoir.Plumbing is provided to couple the reservoir to the venturi at the waterjets. Then, negative pressure created at the venturi during water jetoperation causes the condensate to be sucked from the heat pump 50 andprovided into the spa tub. Alternatively, the water pump 54 for thetherapeutic jets may be configured with plumbing 72 to pump suchcollected condensate into the spa tub 12, e.g., via one or more of thejets 32. In yet another alternate embodiment, a separate dedicated pump74 is provided to remove the condensate and provide it into the spa tub.By removing the condensate from the mechanicals of the heat pump system,indoor use of the system will not result in any water damage fromcondensate produced by the ambient heat exchanger.

In accord with another preferred aspect of the invention, the ambientheat exchanger 58 automatically cycles off and on periodically duringoperation. Without such cycling, the coils of the ambient heat exchangermay become built-up with frost as humid air is blown across the coolcoils, greatly reducing the efficiency of the system or even causingextended periods of shutdown while the coils are defrosted. Cyclingkeeps the coils free of frost.

In accord with a yet another preferred aspect of the invention,components of the heat pump 50 are subject to noise reduction so thatthe noise is masked from persons seated in the spa tub 12 to preventtheir disturbance. Such noise reduction may include physical masking byacoustical isolation and/or insulation. For example, the compressor andother components may be acoustically isolated from the spa tub shell 12and cabinet 40 via an acoustic panels, acoustic thermal batting,acoustic foam, Thinsulate™ hydrophobic acoustic insulation, and/or othermaterials that provide acoustic attenuation. In addition, components ofthe heat pump 50 may be mounted to the underside of the spa shell and/orwithin the cabinet using vibration-absorbent coupling elements,including, but not limited to, rubber washers. Alternatively, the noisereduction may be implemented electronically, via an active noisereduction system which generates sound waves out-of-phase with the soundwaves (noise) generated by the heat pump 50 and preferably thehydrotherapy jet system 30 as well. Exemplar active noise reductionsystems are described in U.S. Pat. Nos. 5,384,853, 5,434,925 and5,559,893, which are incorporated by reference herein in theirentireties. In accord with another preferred aspect of the invention,the user interface 80 for electronically operating the controller 102 ofthe heating and cooling operations and the water pump 38 forhydrotherapy systems is located along the rim 28 of the spa tub shell atan opposite side of the tub from where the heat pump 50 and water pump38 are located. Primary users of the hot tub typically sit in seatsadjacent the interface 80 for ease of operation of spa tub systems andsuch seats therefore are at a maximum distance from heat pumpcomponents, thereby locating the primary users of the tub and the sourceof noise generation at maximum distances from each other.

In accord with a further preferred aspect of the invention, the spa tubshell 12 and cabinet 40 together define a space 82 therebetween. Heat isco-generated by the water pump 38 and the compressor 52 of the heat pump50 and the hot air is collected within the space 82. In a heating modeof operation, the air in the space 82 can be directed by a diverter 84to ambient heat exchanger when the air in the space is warmer than theambient air. Then, when ambient air is warmer than air in the space 82or when pulling air from the space would result in other thermalinefficiencies (e.g., excessive cooling of the spa tub water, as suchair operates to insulate the water), the diverter 84 is automaticallyredirected to pull ambient air.

In addition, such co-generated heat in space 82 can be made available tothe air supply 39 for the jets 32 via use of check valves mounted on thejet valve bodies, as disclosed in U.S. Pat. No. 5,850,640 or through anair valve coupled, e.g., via manifold, to the air plumbing through whichair is plumbed to the venturis at the jets. Thus the entrained air ismore comfortable to the users of the spa.

The spa preferably includes an ozonator 86, which is known in the art tocontrol bacteria and otherwise filter the water. The standard locationof the ozonator 86 within the space 82 defined between the spa tub shelland cabinet is particularly humid. However, the ozonator requires aninfusion of dry air for optimal operation, as dry air accepts more ozonefor delivery to the water. Therefore, in the prior art, operation of anozonator in a conventional spa tub may be less than optimal. In accordwith another aspect of the invention, drier air from the cool side ofthe ambient heat exchanger 58 of the heat pump is drawn off and sent tothe ozonator to optimize operation of the ozonator.

In accord with an additional preferred aspect of the invention, the spaalso includes a conventional electric resistance heater 90 that can beactivated in conjunction with the heat pump 50 as an auxiliary heater toprovide a rapid heating or turbo mode. In turbo mode operation, theheating system uses approximately 6.5 kW of power. Because the water isbrought up to the desired temperature more rapidly, the spa tub may beused sooner after activating the controller 102 (FIG. 5) (via theinterface 80) to increase the water temperature to the desired highertemperature from the starting temperature. In one embodiment, shown inFIG. 4, a portion of the heat pump water heat exchanger 54 is integratedwith the heater coil 92 a of the electric resistance heater 90 a. Inthis embodiment, the coils of the water heat exchanger 54 are containedwithin the heater unit and the resistance heater coils 92 a wrappedaround the outside of the water heat exchanger 54, or vice versa. Suchprovides the advantage of both space savings and cost savings. The costsavings can be significant where the shell of the water heat exchanger54 is an expensive material such as titanium. In this case only onetitanium shell would be required. Once at the desired temperature, theelectric resistance heater 90 a would shut off, allowing the more energyefficient heat pump to maintain the water temperature.

As essentially all spa tub systems currently in service include anelectric resistance heater, the heat pump 50 is ideally suited as aretrofit module for placement within spa tubs already including aresistance heater. Such retrofit can be performed by a technician onsiteat an install location. The addition of the above described heat pump toa spa tub already including an electric resistance heater provides acost efficiency way to achieve the benefits discussed herein; i.e.,overall energy efficiency, rapid heating mode, and cooling mode.

Turning now to FIG. 6, an example of a spa system is shown having anexternal heat pump 124. Such a system allows a spa system 122 to beretrofit to take advantage of the benefits of the heat pump 124. Inthese systems, the heat pump 124 can be mounted on the outside of thespa cabinet or located at a distance therefrom. Moreover, externalplacement of the heat pump 124 allows the heat pump to be built intofunctional elements adjacent or near the spa for users of the tub toenter/exit the tub or relax outside the tub. By way of example, suchfunctional elements may include one or more of steps, a seat, a benchand/or a planter, which can form a housing for all or portions of theheat pump. The heat pump 124 includes a compressor, a water heatexchanger, an expansion device, an ambient heat exchanger, connectiveplumbing, a four-way valve, and a working fluid (refrigerant). In oneembodiment, the water is circulated out of the tub and cabinet of thespa system 122 through plumbing 126 to the water heat exchanger of theheat pump 124 and back into the cabinet to the plumbing therein torecirculate to the jet assemblies. In an alternative embodiment, thewater heat exchanger is provided within the spa tub cabinet and therefrigerant is plumbed through the heat pump 124 through the plumbing128 to the water heat exchanger within the spa tub cabinet to modify thetemperature of the water as necessary.

Turning now to FIG. 5, an exemplar electric circuit 100 for activatingvarious functions of the temperature control system is shown. Thecircuit 100 is activated via signals from the controller 102, which istriggered by input at the user interface 80 and a thermostat 104. Thecircuit 100 shown includes four relays (main power relay 106, compressorrelay 108, heat/cool mode relay 110 and turbo mode relay 112), althoughother circuitry may be provided. The main power relay 106 in ON positionprovides two 110V lines, P1 and P2 to the turbo mode relay 112, and onlyP1 (110V) to the compressor relay 108. The compressor relay 108 in ONposition provides power to the compressor 52 when both the main powerrelay 106 is also ON. The heat/cool mode relay 110 in ON positionactivates the solenoid in the 4-way valve 62 to configure the valve froma neutral heating mode to an activated cooling mode. The turbo moderelay 112 in ON position provides 220V power to the electricalresistance heater 90 so as to power on the resistance heater incombination with the heat pump to effect the turbo mode of operation ofthe temperature control system. The controller 102 signals each of therelays 106, 108, 110, 112 to be in the appropriate position for theselected mode of operation. TABLE 1 Relays Relay Main CompressorHeat/Cool Turbo Mode Position OFF OFF OFF = Heat OFF System InactivePosition ON OFF OFF = Heat OFF Power enabled for heat pump or heatingand cooling modes, but ON = Cool neither mode operating; WaterTemperature at Set Temperature Position ON ON OFF = Heat OFF Heat PumpHeating Mode Position ON ON OFF = Heat ON Turbo Mode Heating Position ONON ON = Cool OFF Heat Pump Cooling Mode Position ON OFF OFF = Heat ONAuxiliary Resistance Heater Only or ON = Cool

The system may include a clock timer that is set via the user interface80 to automatically bring the water to a desired temperature at a settime. Depending on how far in the future is the set time, either theheat pump alone (for more energy efficiency), or the heat pump incombination with the electric heater (i.e., turbo mode) can be used tobring the water to the desired temperature such that it reaches thedesired temperature by the set time.

In accord with the above, the clock timer of the control system allowsthe user to preprogram a time at which the spa water is to reach aspecified temperature. The clock timer may be an analog or digital clockthat allows the user to program the control system to activate heat pumpand/or electric heater (collectively, water temperature modificationsystem) at a specific time on the current day or future date. By way ofexample, the clock timer can be a digital clock with twelve hour AM andPM settings or a 24 hour clock. Such clock timer can include programmingcontrols similar to an electronic thermostat for setting homeenvironment temperatures; i.e., permitting the user to set a time atwhich the spa tub water is to be a particular user set temperature, andoptionally a day of the week for such settings. The clock timer mayinclude multiday programmability, and the clock timer and user interfacemay be used to program the control system to activate the watertemperature modification system at a regular schedule. As examples, theuser can preprogram the control system to activate the water temperaturemodification system to bring the water to a set temperature every Fridayevening at 7 PM or alternatively to activate at regular times on aweekend schedule. In addition, the clock timer may include a usersetting or default setting for the length of time for which the water isto be maintained at the set temperature, e.g., one hour.

Alternatively, the clock timer may simply activate the water temperaturemodification system, e.g., the turbo mode operation, to begin operationat a user set time, as opposed to reach a temperature at a user settime.

In accord with yet another preferred aspect of the invention, thecontrol system includes a memory that stores data related to watertemperature and the time required to raise and lower the water to a userinput temperature. Additional data may also be stored including mode ofoperation, ambient temperature, etc. The data is used by the controlsystem to determine the most efficient way to raise or lower the tubwater to the temperature set by the user, particularly at the presenttime.

As the database of information grows, the database becomes more accurateallowing the system to perform more efficiently. The spa tub systemreferences the database each time the user enters a set point for thetime and/or day on which the user wants the spa water to reach aparticular temperature. Information from the database is then analyzedby the system to determine how far in advance the control system shouldactivate to begin heating or cooling the spa water depending on thewater temperature and/or other factors. This allows the control systemto activate the heat pump at the optimal time to adjust the temperatureto reach the desired temperature at the present time.

The optimal performance time for advance activation may vary dependingon the water temperature, ambient temperature, and heater/coolerefficiencies. For example, in mid-summer, the time needed to heat thespa water by ten degrees from a temperature of 90° F. might be threeminutes. Therefore, the optimal time determined by reference to thedatabase of the spa system becomes 3 minutes prior to the temperatureset point input by the user. However as an example, on a winter day, theoptimal time needed to heat the same body of water by twenty degreesfrom a temperature of 80° F. might be 12 minutes rather than 6 minutesdue to the effects of ambient conditions on the spa water. In thisexample, the optimal time determined by reference to the database of thespa system would be 12 minutes prior to the temperature set point inputby the user. The database collects information over time related totime, temperature, and date so that the system improves on thedetermination of the optimal time with increased use.

Turning now to FIG. 7, one aspect of the operation of the temperaturecontrol is provided. When a user desires the spa water temperature toreach a desired level at a particular time and/or day, the user firstsets the clock timer at 130, inputting the user set time and user settemperature into the user interface on the spa system. The controlsystem then determines at 132 the optimal time to begin heating the spatub water to reach the user set temperature by the user set time.Preferably, the control system activates at a time which providesefficient operation; i.e., bringing the water to the desired temperatureat the set time and not in advance so that energy is wasted. Thisdetermination is preferably carried out by measuring at 134 thetemperature of the tub water at predetermined intervals prior to theuser set time and referencing at 136 the database of past performance.If there is in sufficient data in the database from system operations,the database preferably uses preloaded baseline data; i.e., factorydefaults, to initially provide efficient operations. Based on themeasured temperature and with reference to the database, the controlsystem determines at 132 the optimal time to activate the heat pump (orother water temperature modification system) to reach the user settemperature at the user set time.

Once the system activates at 138, the control system measures the watertemperatures at set intervals and determines at 140 whether the measuredtemperature is between system tolerance limits. These limits arepreferably preprogrammed in the control system, but may be optionallyset by the user, and are typically between +/−1° F. of the user settemperature. If the measured temperature is within the tolerance limits,the system either (i) deactivates at 142 the heat pump for improvedenergy performance and re-measures the temperature of the spa water at asystem programmed time interval (preferably between 1 millisecond and 1minute) or (ii) maintains at 144 the heat pump operational in a lowenergy mode for improved temperature stabilization. Subsequenttemperature measurements are taken at 146. If the water temperature ismeasured to be outside the temperature tolerance limits at 140, the heatpump is activated at 148 to adjust the temperature of the spa wateruntil measured at 140 within the tolerance limits. The heat pump is thendeactivated at 142 or placed into a low energy temperature stabilizationmode at 144. Additionally, if the water temperature rises higher thanthe user set temperature (e.g., due to external or environmentalfactors), it is recognized that the heat pump can be operated in itsreverse cooling mode until the water temperature is reduced to withinthe tolerance limits to further stabilize the temperature. Suchtemperature stabilization function provides a safety feature to thesystem. The algorithm continues until a shut-off signal is received at150 either by manual control or from the clock timer, described above,which terminates at 152 the system temperature regulation. Use of thisalgorithm by the control system can maintain the spa water temperatureat the user set temperature until the control system acts on systemshut-off information.

There have been described and illustrated herein several embodiments ofa hot tub spa, heating systems therefore, and methods of heating andcooling spas. While particular embodiments of the invention have beendescribed, it is not intended that the invention be limited thereto, asit is intended that the invention be as broad in scope as the art willallow and that the specification be read likewise. Thus, while aparticular spa design has been shown and described, it will beappreciated that the heating and cooling system and methods can beapplied to other spas as well. Also, the heat pump of the preferredembodiment may be replaced by a number of other water temperaturemodification systems for heating and cooling spa tub water including gasand oil heaters, electric resistance heaters, and electric coolers toname a few. The system and methods described herein are particularlyefficient for larger swim-type spas carrying large amounts of water. Itwill therefore be appreciated by those skilled in the art that yet othermodifications could be made to the provided invention without deviatingfrom its scope as claimed.

1. A spa tub system, comprising: a) a spa tub; b) a hydrotherapy systemincluding a plurality of jet assemblies mounted within the tub, asuction fitting mounted in the tub, plumbing coupling said jetassemblies, and a water pump that can circulate water from the suctionfitting through the plumbing and back into the tub through the jetassemblies under pressure; c) a water temperature modification systemoperatively coupled to hydrotherapy system capable of modifying thewater temperature of water flowing through said hydrotherapy system; andd) a control system coupled to said water temperature modificationsystem to activate the water temperature modification system to maintainthe water temperature of the water between upper and lower temperaturelimits relative to a user set water temperature.
 2. A spa tub systemaccording to claim 1, wherein: said control system activates a heatingmode of said water temperate modification system if the watertemperature is below said lower limit, and activates a cooling mode ofsaid water temperature modification system if the water temperature isabove said upper limit.
 3. A spa tub system according to claim 1,wherein: said upper and lower limits are ±1°F. relative to the user setwater temperature.
 4. A spa tub system according to claim 1, wherein:said water temperature modification system can both actively raise andlower the water temperature of the water flowing through saidhydrotherapy system.
 5. A spa tub system according to claim 4, wherein:said water temperature modification system includes a heat pump.
 6. Acontrol system for a water temperature modification system for a spatub, said control system comprising: a) a user interface allowing userinput of a user set water temperature; and b) a controller that monitorsthe water temperature of the spa water and activates the watertemperature modification system to heat the water when the watertemperature is below the user set water temperature and activates thewater temperature modification system to cool the water when the watertemperature is above the user set water temperature.
 7. A control systemaccording to claim 6, wherein: said controller operates to maintain thewater temperature within a preset temperature range.
 8. A control systemaccording to claim 7, wherein: said preset temperature range is ±1° F.relative to the user set water temperature.
 9. A method of regulatingwater temperature in a spa tub including a water temperaturemodification system relative to a user set water temperature input at auser interface, comprising: a) monitoring the temperature of the waterwith a system controller; b) transmitting a signal from the systemcontroller to a water temperature modification system to automaticallyraise the water temperature when the water temperature is below the userset water temperature; and c) transmitting a signal from the systemcontroller to a water temperature modification system to automaticallylower the water temperature when the water temperature is above the userset water temperature.
 10. A method according to claim 9, furthercomprising: d) maintaining the water within upper and lower temperaturelimits relative to the user set water temperature.
 11. A methodaccording to claim 10, wherein: said maintaining includes deactivatingthe water temperature modification system.
 12. A method according toclaim 10, wherein: said maintaining includes maintaining the watertemperature modification system under constant activation.
 13. A spa tubsystem, comprising: a) a spa tub; b) a hydrotherapy system including aplurality of jet assemblies mounted within the tub, a suction fittingmounted in the tub, plumbing coupling said jet assemblies, and a waterpump that can circulate water from the suction fitting through theplumbing and back into the tub through the jet assemblies underpressure; and c) a heat pump including a water heat exchanger, whereinthe water pump circulates water contained by the tub through the waterheat exchanger to heat the water.